Flotation of iron ores



iron enriched product.

Patented Aug. 28, 1945 FLOTATION OF IRON ORES Julius Bruce ClemmerTuscaloosa, of America, the Interior and Ballard H. Clemmons, Ala.,assignors to the United States as represented by the Secretary of NoDrawing. Applicatlon January 22, 1943, Serial No. 473,162

19 Claims.

(Granted under the act of amended April 30, 1928;

This invention described herein may be manufactured and used by or forthe Government 1 for governmental purposes, without the payment to us ofany royalty thereon.

This invention relates to an improved process for the concentration ofiron ores whereby froth flotation of the siliceous gangue constituentsyields an iron enriched product; more particularly it relates to a frothflotation process for siliceous gangue constituents in iron ores,employing anionic reagents.

An object of the invention is the development of an improved flotationprocess for the concentration of natural oxides of iron from pulps containing them in the presence of siliceous gangue. A'further object is toprovide a flotation process for separating silica from iron oxidesemploying anionic reagents. A still further object is to provide aflotation process for concentrating iron ores or products containingboth calcareous and siliceous materials. Still other objects include thedevelopment of a flotation process which will have greater selectivityin separating siliceous materials from iron ores and thereby effectgreater economies. Other objects, purposes, and advantages of theinvention will hereinafter more fully appear or will be understood fromthe detailed description of its practice.

We are aware that various methods have been proposed for theconcentration of iron ores by flotation methods for the purpose ofrejecting siliceous gangue constituents and recovering an The mostcommon method known to the art for concentrating iron ores has been tofloat the iron oxides from the siliceous gangue constituentsemploying ananionic col lector, such as oleic acid or sodium oleate, in conjunctionwith auxiliary reagents, as soda ash or sodium silicate, to retardflotation of the silica. Those skilled in the art recognize that themethod has limitations. The method yields good results on some ironores, but is not applicable to others. Desliming of the, ore pulps isgenerally necessary before good flotation of the granular oxides can beeffected, and the pulps must be relatively free of'soluble salts. Thesalts, such as lime or magnesia, derived from the ore or present in thewater employed, activate the siliceous mineral to flotation with thesoap collectors and results in poor selectivity. Soft water relativelyfree of lime.

v ham district, Alabama.

iron oxides which would be lost March 3, 1883, as 37-0 0. G. 757) and.magnesia is generally required for satisfactory iron oxide flotation.

'An alternative method for concentrating iron ores by flotation has beento reverse'the separation and float the siliceous gangue minerals fromthe iron oxides by employing cationic collectors. The application ofsuch reagents to iron ores has been described by Kirby and Gillson inUnited States Patents Nos. 2,217,684 and 2,221,485. This method isattractive in that iron ores in general contain less siliceous materialthan iron oxides, and flotation of the silica is in keeping with thepreference of floating that constituent which occurs in least amount.Cationic reagents are not without their limitations, being, in general,more expensive than those of the anionic type. The cationic collectors,moreover, are not particularly selective, nor are they effective silicacollectors in the presence of slime iron. Desliming of the iron orepulps is usually necessary before acceptable flotation of silica can beachieved with cationic collectors. On many iron ores desliming resultsin a serious loss of iron. The iron oxides are relatively soft andfriable as compared to siliceous gangue constituents, and grinding thesilica to flotation size unavoidably slimes much of the if deslimingwere practiced.

The lack of a suitable flotation method for concentrating iron ores haslong been apparent to those engaged in the art. The customary flotationmethods, previously discussed, have many limitations and are notapplicabie to all iron ores. These methods give poorest results on thoseore or products most in need of concentration, that is, fines resultingfrom treatment of iron ores by other methods of concentration. Asatisfactor; flotation method for recovery of the fine iron oxides andrejection of the silica would be of ma terial aid for the concentrationof those iron ores which slime readily on grinding or require finegrinding for liberation.

The need of a feasible flotation method for iron ores wasparticularlyapparent in the concentration of the'red iron ores' of theBirming- These ores consist essentially of hematite associated withquartz and calcite, with minor amounts of other siliceous and calcareousmaterials including ferruginous clay. The red ores require relativelyfine grinding for and calcareous materials.

the liberation of the hematite, and the hematite is soft and slimesreadily. Wet concentration methods, such as hydraulic classification andtabling of the red iron ores, enables recovery of the coarse hematite ina product of acceptacle silica content. The fines resulting from suchtreatment are contaminated with too much silica and require processingby other methods such as flotation, to reject the silica and recover anacccptable iron product.

A satisfactory flotation method for the recovery of hematite andrejection of the silicain the red iron ores or concentrator lines wassought. Flotation of the iron oxides from the silica with anioniccollectors, and flotation of the silica from the iron oxides withcationic collectors failed to give the desired results. Much of thesilica floated with the hematite when using anionic collectors and gavelow grade iron concentrates. The silica, predominantly quartz, wasapparently activated to anionic flotation due to the presence of limesalts in the ore. Attempts to deactivate the silica and prevent itsflotation with the hematite were not successful. Reversing theseparation and floating the silica from the iron oxides with cationiccollectors was not encouraging. The contaminated silica was reluctant tofloat with cationic collectors and much remained in the iron product.Neither of the methods customarily employed on iron ores wassatisfactory, and other means of perfecting the separation was sought.

By extended research and experimentation, we discovered that we couldmake use of the acticated condition of the silica and effect itsflotation from the hematite and calcite with anionic collectors whileretarding flotation of the hematite with a metaphosphate in a stronglyalkaline pulp. A moderate amount of meta-, hexameta-, or polyphosphateis effective in retarding flotation of iron oxides and calcareousmaterials when used in pulps made strongly alkaline with sodium orpotassium hydroxides, or their equivalents.

or'es of the Birmingham district containing calcareous as well assiliceous gangue materials. A variety of ores and mill products from thedistrict have responded readily to the method.

The calcareous materials, largely calcite, may be floated with thesilica or retarded with the hematite by choice of the amount ofmetaphosphate employed.

A prime requisite in our method of flotation of silica from iron ore isthat the pulp be dispersed. The metaphosphates in the strongly alkalinepulps are effective slime dispersants as well as selective depressantsfor the iron oxides Supplementary reagents such as sodium silicate,dextrin, starch, various tannins, or ortho or pyrophosphates may be usedas dispersants in conjunction with reduced amounts of metaphosphate. Thepyrophosphates, when flotation of the calcareous materials is-sought,are particularly advantageous.

in conjunction with metaphosphate. These rehave been used on varioustite and must be used in conjunction with a metaor polyphosphate.

The discussion heretofore relates to the flotation of silica from ironores in which the silica was naturally activated to anionic flotationdue to the presence of soluble salts. The highly siliceous and weatherediron ores of the Birmingham district are relatively free of solublesalts and the silica is non-activated. On such ores the silica requiresprior activation before acceptable flotation can be achieved by ourmethod Extended research on a variety of siliceous iron ores from boththe Alabama and Lake Superior districts has demonstrated that our methodlends itself well to the use of silica activating agents. Conditioningthe ore pulps with a moderate amount of a metal salt selected from thegroup which form soluble basic or complex salts in strongly causticpulps in the presence of metaphosphate, activates flotation by the fattyacid or soap collectors without adversely effecting subsequentretardation of the iron oxide. Such metal salts as calcium chloride.strontium nitrate, barium chloride, zinc sulfate, aluminum sulfate, orlead nitrate iron ores for activation of the siliceous gangue and foundsatisfactory. Of these lead nitrate was most effective and waspreferred. Calcium chloride and slaked lime were used on many oresand'gave good results. From the standpoint of cost, slaked lime wasparticularly attractive. When using lime as the activator, best resultsw'eresecured by adding the lime to the grinding operation in an amountsumcient to give a resulting grind water with a pH of about 11. 'Theground pulp wasflocculated and settled readily. The grind watercontaining excess free lime was discarded and the solids repulped withfresh tap water and floated to reject the silica. Free lime isdetrimental in the separation and must be avoided. Washing the pulp freeof lime reduces the subsequent phosphate requirements in flotation. Amoderate amount of free lime in the flotation pulp can be overcome byconditioning the pulp with soda ash to precipitate the lime as insolublecarbonate. The caustic alkalinity developed reduces the subsequentcaustic requirements.

The invention will be further illustrated but is not intended to belimited by the following examples:

Example I A sample of iron ore was obtained from a mine in the GracesGap area, near Birmingham, Alabama. The ore was typical of the districtand contained hematite associated with a gangue composed predominantlyof quartz andcalcite with minor amounts of accessory calcareous andsiliceous materials including ferruginous clay. A head analysis gave33.? percent Fe, 11.8 percent CaO, and 28.1 percent insoluble. The orewas stage crushed to pass 20 mesh and used as the feed for subsequentflotation procedures.

A 250-gram portion of the ore was wet ground in a one-gallon pebble millto pass mesh using 4500 grams or flint pebbles as the grinding media andone liter of tap water. The ground charge was alkaline (pH8.6) andqualitative tests on the grind water showed presence of lime salts. Theground charge, including slime, was transferred to a small mechanicalagitation flotation cell of standard design using grind water as the thesilica suflicient for its "8,883,467 media. The resulting pulp forflotation contained 20 percent of solids.

Flotation of the silica from the hematite and calcite was effected bythe following reagents expressed in conventional terms of pounds per 4ton of ore: g

The pulp was conditioned with the sodium hydroxide and sodiumhexametaphosphate for. 2.5 minutes prior to the addition of the talloelwhich served as the silica collector. The talloel was emulsified intothe'pulp by conditioning an additional 1.5 minutes. .Air was thenallowed 'to enter the cell and resulted in an' immediate formation of acompact, heavily mineralized froth of the siliceous material which waslargely quartz. The froth was collected for a period of 5 minutes whenflotation was completed. The rougher froth was twice cleaned byrefloating in the same cell using tap water of moderate hardness andadditional sodium hydroxide and sodium hexametaphosphate as indicated.final silicareject, conventionally referred to as concentrates butdesignated here as "rejects since they are the waste product,.thecombined middlings', and the iron concentrates, conventionally referredto as tailings in ore dressing terminology but designated here asconcentrates since they represent the economic iron product, were dried,weighed, and analyzed.

The silica reject accounting for 19.8 percent of the weight of thecharge, assayed 6.3 percent Fe, 4.7 percent CaO, and 82.1 percentinsoluble, and represented a rejection of 57.9 percent of the totalvinsoluble in the ore. Combining the flotation middlings and ironconcentrates gave a composite iron product accounting for 80.2 percentof the weight of the charge, assayed 40.5 percent Fe, 13.6 percent CaO,and 14.8 percent insoluble, and represented a recovery of 96.3 percentof the total iron in the ore.

The above mentioned test was about average" of a large number made ontheore'. Grinding the ore to 65 mesh or 200 mesh in either a pebble millor iron ball mill gave results entirely similar to those alreadyrecorded. In every case good flotation of the silica was achieved whenthe. pH of the pulp was maintained between and 12 by the addition ofsodium hydroxide, caustic soda, lye, or similar alkalies. Ammoniumhydroxide was also used in other tests but is less used as the collectorfor the activated quartz in the recorded test. Similar results wereobtained when using oleic acid or sodium oleate. A combination oftalloel and oleic acid is particularly effective.

Example 11 g A 250-gram charge 01 the Graces Gap area iron ore wasground to pass 100 mesh as in Example I. The ground charge was deslimedby sedimentation methods and the granular portion floated to rejectsilica. Sodium hydroxide'and sodium hexametaphosphate were used toalkalize the pulp and retard flotation of the hematite and calcite. Theamounts employed were 1.0 and 0.6 pound per ton of ore, respectively, inthe roughing ton in the olelc acid operation, and 1.0 and 0.12 pound percleaning operation. Talloel and crude were used as the collectors in the'roughing operation in amounts equivalent t 0.8

and'0.4 pound per ton respectively. An additional 0.4 pound per ton oftalloel and 0.2 pound '80 The per ton oi lead nitrate were used to floata scavenger product which was subsequentlycombined with the rougherfrothand double cleaned to yield the final reject. The test productswere dried, weighed, and analyzed. The slime fraction accounted for 23.5percent of the weight and contained 282 percent of the total iron in theore. portion yielded a silica reject product assaying 6.4 percent Fe,8.2 percent CaO, and 75.9 percent insoluble, and represented a rejectionof 64.1 percent of the total insoluble in the ore. The iron concentratesassayed 47.6 percent Fe, 10L8 percent CaO, and 9.8 percent insoluble,and accounted for 47.6 percent of the total iron in the ore. Combiningthe flotation middlings, iron concentrates, and slime gave a compositeiron product representing a-recovery of 95.5 percent of the total ironin'a product assaying 42.9 percent Fe, 12.2 percent 030, and 13.3percent of insoluble. I

Although desliming is not necessary in our method for successfulflotation of silica from iron ores, it is helpful and should bepracticed whenever possible.

attractive from the cost standpoint and difliculty involved inhandling.

Sodium hexametaphosphate was used as the hematite and calcite retardantsin the test. The

mono-sodium metaphosphate, or its polymeric forms may also be used. Thealkali metal salts of the tetraphosphates are also effective forretardation of iron oxides in quartz flotation when used in stronglyalkaline pulps. The orthoand pyro-phosphates are ineffective iron oxidedepressants, but have been used as supplementary dispersants inconjunction with the meta com pounds. Talloel, an impure mixture ofrosin and fatt acids obtained from paper mill black liquor,--was ExampleIn Conditioner Rougher Caustic soda Sodium metaphosphate. Tetra sodiumpyrophosphato. Crude sodium oleate. Crude oleic acid Pine oil Depressionof the hematite was effected by sodium metaphosphate and tetra sodiumpyrophosphate in a pulp made all saline (pH'-10.9l

Flotation of the granular and ironconcentrate gave iron, 0.5 percentCaO,

with caustic soda. Sodium oleateand oleic acid were used as the.collectors for the silica and calcite. The rougher froth was doublecleaned for the final reject. Test products were dried, weighed, andassayed.

The reject product represented 50.0 percent of the weight and assayed14.7 percent Fe, 30.5

percent CaO, and 10.7 percent insoluble. The lime and insolublereiection were 86.1 and 53.9 percent respectively. The iron concentratesassayed 57.3 percent Fe, 2.0 percent C80, and 9.7 percent insoluble. andaccounted for. an iron recovery of 4'7 .1 ercent. Combining theflotation middlings and iron concentrates gave a commits iron productrepresenting a recovery of 78.4 per.

- cent of the total iron in a product assaying 53.4

percent Fe, 4.9 percent CaQ and 9.1 percent of insoluble. I

Example I V A siliceous red iron ore was obtained item the Graces Gaparea in the Birmingham district, Alabama. A head analysis gave 42.3percent Fe, 0.5 percent CM), and 31.3 percent insoluble. The samplediffered from those previously considered in that the silica, largely as.quartz. was non.- activated.

A 250-gram representative portionof the ore was ground in aone-sallonironball mill to pass Cleaver ;Conditioner B01 8 i 1 v 2Sodium hydrk l)xide .t .1.1 7 1.0 0.2 0.2

di exame a 0.8.- 80 um p 0.0 0.08 1.,0. g 11.2 10.6 10.6 .6

Y The silica activated by slaked lime floated heavily hiineralizedfroth.

rapidly in a compact,

double cleaned using tap The rough froth was water and additionalreagents tor a final reject.

The floated material assayed 5.0 percent Fe, and 91.2 percent insoluble,and represented a'rejection of 51.3 percent of the total insoluble inthe ore. The iron concentrates assayed 53.4 percent Fe and 13.5 percentinsoluble, and accounted for a recovery of 80.7 percent of the totaliron in the ore. Combining the flotation middling a composite ironproduct representing a recovery of 97.9 percent of the total iron in aproduct assaying 50.3 percent and 18.5 percent insoluble.

Similar tests in-which lead nitrate, barium chloride, calcium chloride,or copper ammonium sulfate were used as the silica activator gaveequally good results. From. 0.5 to 4.0 pounds of the metal salt per tonof ore was required for complete activation of the silica. The preferredprocedure when using the metal salts as activators is to condition theore pulp. amount or alkali and. metaphesphate to. reload with thedesired cent insoluble was tested by flotation.

amid the hematite and give a dispersed pulp with a pH of 10 to 12. Themetal. salt was. added to the pulp and conditioned. 2-.5 to minutes :01-lowed by the addition or the collector tor flotation of the silica.Reversing the order or addition of activator and collector ispermissible and may even give improved results on certain ores. Amixture of alkali, phosphate, metal salt, and collector prepared byadmixing outside the cell has been used to float the silica fromdeslimed iron ore pulps with good results. The soluble metal soapcomplex served both as collector and activator for the silica.

Example V A sample of Mesabi range iron ore washer tailmas c ma-mine.3&5 percent Fe. and 52.0 per- The silica. lar ly present as quartz, wasessentially finer than 0 mesh.

A. ZMFBXam p rtio or the sample was blunged .5 minutes in a flotatio cll with 5.00 co. or. tap water and slaked l me equivalent to 12 poundsper ton of ore. The pH of the slurry was. 11.0. Tbsslurry was withdrawnfrom the. cell and washed. twic with fresh tap water by decantation toreject. the excess lime salts, taking care to avoid loss of slime in theoperation. The limetrcatfid slurry was repulped with fresh tap water andfloated to reject the silica using the generalized procedure, describedin Example I.

The reagent charge employed wa as follows:

Cleaner Conditioner Rougher Sodiumhydroside l. 2 0. 5 0. 4 Sodlumloxametaphosphate l. 0 0. 2 0. 1 0. 1 'Ialloel 1. 4 0.2 Lead nitrate 0.2pH, of. pulp l1. 0 l0. 3 l0. 6 10.8

Good flotation or the silica was achieved. The rejects assayed: 10.3.percent Fe and 83.8 percent insoluble, and represented 90.8 percent ofthe insoluble in the ore. The iron concentrates assayed 61.0. percent Feand 8 .1 percent insoluble and represent a recovery of 50.2 percent ofthe total iron in the ore. Flotation or the silica. increased the ironcontent 29.5 percent and deereasedthe insoluble content 43.9 percent.Comhim. the middlings with the iron concentrate have a composite ironproduct representing a recovery oil 8126. percent of the total iron in aproduct; assaying 58.81 percent Fe, and 10.95 percent of insoluble.

Example VI A sample of slime filter cake from a gravity concentrator inthe Birmingham district; Alahams". as test d by our method to rejectsilica and recover an iron enriched. product. The

sample assayed 41.6. Percent. Fe, 8.8 percent CaO,

to the flotation cell and floated using the procedure described inExample I.

Flotation of the quartz was. achieved with the following reagentsexpressed in conventional terms of pounds per ton of solids.

d1 Cleaner on Rouglier Sodium carbonate 1.0' Sodium hydroxide 0.6 0.20.2 0.2 Sodium hexametaphosphetc 0.4 0.04 0.04 0.08

Sodium oieate" 2.0 Oleic acid 0.96 pH oip'ulp 11.1 10.6 10.5 10.7 10.8

The pulp was conditioned 2.5 minutes with sodium carbonate toprecipitate remaining lime salts prior to floating'the activated quartzwith sodium oleate and oleic acid from the strongly akaline dispersedpulp. The rougher froth was triple cleaned for the final silica rejectproduct. The silica reject, accounting for 10.3 percent of the weight ofthe dry sample, assayed 6.2 percent Fe, 6.2 percent C80, and 76.4percent insoluble, and represented a rejection of 40.6 percent of thetotal insoluble in the sample. The low rejection of insoluble maybeuattributed to the relatively large amount of ferruginous .clay in thesample which does not float with the quartz.

The iron' concentrates assayed 47.1 percent Fe,

8.3 percent CaO, and 12.7 percent insoluble, and

accounted for 86.5 percent of the total iron pr'es-' ent in the sample.Combining the flotation middlings and iron concentrates gave a compositeiron product representing a recoveryof 98.5 percent of the iron andassayed 45.7 percentFe, 9.1 percent CaO, and 12.8 percent insoluble,

Laboratory batch flotation tests on the concen-. trator filter cake weresupplemented by continuous flotation tests on a pilot plant scale at theplant. The product treated was a deslimed portion of fines bledcontinuously from the plant circuit. The tests were successful and demonstrated that our method could be used under continuous operatingconditions to reject free silica from concentrator fines with onlymoderate loss of iron or lime. the continuous runs than in the batchflotation tests. Rapid and complete flotation of the activated silicawas effected with talloel, oleic acid, or sodium oleate when used inconjunction with a moderate amount of a metaphosphate in a stronglyalkaline circuit.

It will be clear from the description of our method and results obtainedin practice as illustrated by the foregoing examples, that thisinvention is useful for preparing concentrates of is not necessary toperfect a separation. Fourthly. it provides a method for rapid andcomplete flotation of siliceous or calcerous materials from iron oxidein a froth which is easily controlled. Fifthly, itprovides a method forflotation or'reJec-- tion of calcareous materials in iron ores. Sixthly,it provides a method for concentration or a wide variety of iron oresand plant products. Conversely, the process may be used to recoverquartz orsiliceous products of high purity, when the principalcontaminants are iron oxides or calcareous materials.

With the exception of calcareous iron ores such asthose of theBirmingham district, an activator is necessary to insure flotation 01'the silica.

-We have found that the quartz in certain calcareous ores is naturallyactivateddue to its long contactwith lime salts present in the ore. Wehave also found that -while the addition of an activating substance isnot necessary with such ores, a small amount of an activating substanceLess reagents were required in i acceptable iron content from orescontaining too little iron to be normally of technical value. The methodis applicable to ores and waste products containing calcareous as wellas siliceous gangue materials and is sufliciently flexible to permitrejection or recovery of the calcareous materials with the iron oxidesas desired.

.'sorption of metal such as lead nitrate, barium chloride, calciumchloride or the like will often improve the results obtained. Weathered,highly siliceous ores from the Birmingham-district, some ores from theLake Superior region and other highly siliceous ores are found whichseldom contain sufllcient linsa or other soluble salts to activate thesilica an activator be employed in order to float the silica inaccordance with the procedure which we have described above.

Those skilled in the art will understand that there may be severalexplanations for the results which-we obtain, and while we do not wishto bind ourselves to any particular explanation, we postulate theability of metal salts to activate quartz to anion flotation as beingdue to the adions by the quartz, and, in turn, the reaction of suchmetal ions with a soap or like collector to form a relatively insolublesoap coating on the quartz surface which is water repellent and airavid. This explanation would as-' sume that the purer the quartz surfacethe more readily the metal ions are adsorbed, and the resuits which weobtained seemed to show that this is the case. Impure or contaminatedquartz surfaces are much less active in adsorbing metal ions apparentlydue to the fact that the surfaces are already satiated. Absolutely purequartz surfaces are, of course, seldom, if ever, found. New surfaces canbe produced bygrinding but such new surfaces become contaminated as soonas formed by the release of soluble salts. Older methods attempted forthe concentration of iron ores by flotation sought to inhibit thecontamination of newly formed quartz surfaces but in the case of ourprocess this is not essential as contaminated quartz surfaces willassist rather than inhibit the operation of our process.

The anionic flotation reagent is of a class consisting of fatty acidsand soaps and those which we have found most effective are oleic acid,redoil (crude oleic acid), purified and crude sodium resinate, impurerosin acids (derived from talloei from paper mill black liquors),sulfate soap (saponifled talloel) and various talloels. We prefer to usetalloel as the collector in conjunction with a small amount of oleicacid to control the froth.

We wish to caution those skilled in the art that an excess of theanionic flotation reagent seems to inhibit the flotation of-theactivated silica; and it is apparently desirable that only just enough@Qi 50011111 1 oleate or the like be employed on such ores it is highly.essential that an ore to. secure satisfactory flotation. We postulatethis effect to be due to double coatings on the silica surfaces whichare water wetted. It appears that the first coating has the polar groupjoined to the anchored 'metal ion in the quartz surface and thenon-polar or lipophilic end of the collector molecule orientatedoutward. The second coating is then reversed, the two hydrocarbon orlipophilic ends being joined together and th polar end orientated to thewater interface. This explanation seems logical and epparentlyflts thefacts although we do not wish to be bound thereto. We wish to point outthat an excess amount of soap may possibly exert a detergent action onore formed soap coatings to thereby remove them but this explanationappears less likely than that of the reversed or double coatings.

While we have disclosed the preferred embodiments of .our invention, .itwill be readily apparent to those skilled in the art that manyvariationsand modifications may be made therein without departing from the spiritvof the invention.

What we claim as new and desire to protect by United States LettersPatent is:

1. A process for the beneficiation of iron ores which comprises blungingan aqueous comminuted iron ore pulp in the presence of an alkali-solublecompound of an inorganic anion combined with a polyvalent metal selectedfrom the group consisting of alkaline earth metals and heavy metals,establishing a strongly alkaline pH of at least 10 in said ore pulp andthen subjecting said alkaline, activated ore pulp to agitation withaeration in the presence of an anion-active collecting agent selectedfrom the group consisting of fatty acids, resin acids and soaps derivedfrom such acids, and a phosphate compound selected from the groupconsisting of metaphosphates and polyphosphates, whereby siliceousgangue is floated and beneficiated iron ore is depressed and recovered.

2. A process for the beneficiation of iron ores which comprises blungingan aqueous comminuted iron ore pulp in the presence of an alkali-solublecompound of an inorganic anion combined with an alkaline earth metal,establishing a strongly alkaline pH of at least 10 in said ore pulp andthen subjecting said alkaline pulp to agitation with aeration in thepresence of an anion-active collecting agent selected from the groupconsisting of fatty acids, resin acids and soaps derived from suchacids, and a phosphate compound selected from the group ofmetaphosphates and polyphosphates, whereby siliceous gangue is floatedand beneficiated iron ore is depressed and recovered.

3. A process for the beneficiation of iron ores which comprises blungingan aqueous comminuted-iron oxide ore pulp in the presence of analkali-soluble compound of an inorganic anion combined with calcium,then removing excess soluble calcium compounds from the activated pulpand incorporatin .therein sufficient caustic alkali to establish astrongly'alkaline pH of 10 to 12, thereafter subjecting the activated,alkaline ore pulp to agitation with aeration in the presence of ananionactive collecting agent selected from the group consisting of fattyacids, resin acids and soaps derived from such acids, and analkali-soluble phosphate compound selected from the group consisting ofmetaphospirates and polyphosphates, whereby siliceous gangue is floatedand beneficiated, iron ore is depressed and recovered.

4. A process for the 'beneflciation of iron ores which comprises blungngan aqueous comminuted iron oxide ore pulp in the presence of ore pulpto agitation with aeration in the presence of an anion-active collectingagent selected from the group consisting of fatty acids, resin acids andsoaps derived from such acids, and an alkali-soluble phosphate compoundselected from the group consisting of metaphosphates, andpolyphosphates, whereby siliceous gangue is floated and beneflciatediron ore is depressed and recovered.

5. A process for the beneficiation .of iron ores which comprisesblunging an aqueous comminuted iron oxide ore pulp in the presence oflead nitrate, then incorporating therein sufilcient caustic alkali toestablish a strongly alkaline pH of 10 to 12, thereafter subjectings'aid activated alkaline ore pu1p,.to agitation with aeration in thepresence of an anion-active collecting agent selected from the groupconsisting of fatty acids,

- polyvalent metal selected from the group consisting of alkaline earthmetals and heavy metals, establishing a strongly alkalin pH of at least10 in said ore pulp, then subjecting said alkaline activated ore pulp'to agitation with aeration in the presence of an alkali metaphosphateand an anion active collecting agent selected from the group consistingof fatty acids, rosin acids, and scans derived from such acids, wherebysiliceous gangue is floated and beneficiated iron ore is depressed andrecovered.

'7. A process for the beneficiation of iron ores which comprisesblunging an aqueous comminuted iron ore pulp in the presence of analkali-soluble compound of an inorganic anion combined with an alkalineearth metal, establishing a strongly alkaline pH of at least 10 in saidore pulp and then subjecting said alkaline activated ore pulp toagitation with aeration in the presence of an alkali metaphosphate andan anion-active collecting agent selected from the group consisting offatty acids, rosin acids and soaps derived from such acids, wherebysiliceous gangue is floated and beneficiated iron ore is depressed andrecovered.

8. A process for the beneficiation of iron ores which comprises blungingan aqueous comminuted tation with aeration in the presence of an alkali.

metaphosphate and an anion-active collecting agent selected from thegroup consisting of fatty acids, rosin acids and soaps derived from suchacids, whereby siliceous gangue is floated and beneficiated iron ore isdepressed and recovered.

' 9. A process for the beneficiation of iron ores which comprisesblunging an aqueous comminuted .p llp to agitation iron oxide ore pulpin the presence of an alkalisoluble compound of an inorganic anioncombined with calcium, then removing excess soluble calcium compoundsfrom the activated pulp and incorporating therein suflicient causticalkali to establish a strongly after subjecting the activated alkalineore pulp to agitation with aeration in the presence of an alkalimetaphosphate and an anion-active col-, lecting agent selected from thegroup consisting of fatty acids, rosin acids, and soaps derived fromsuch acids, whereby siliceous gangue is floated and beneficiated ironore is depressed and recov-' ered.

10. A process i.'or the beneficiation of iron ores iron oxide ore pulpin the presence of lime, then removing excess soluble calcium compoundsfrom the activated pulp by washing with water and in-- corporatingtherein sufl'lcient caustic alkali to establish a strongly alkaline pHof to 12, thereafter subjecting t e activated alkaline ore pulp toagitation with aeration in the presence of an alkali mctapliosphate andan anion-active co1lect-' ing agent selected from the group consistingof fatty acids, rosin acids, and soaps derived from such acids, wherebyand beneflciated iron ered.

11. A process for the beneficiation of iron ores which comprisesblunging an aqueous comminuted iron oxide ore pulp in the presence oflead nitrate, incorporating therein suflicient caustic alkali toestablish astrongly alkaline pH of 10' to 12, then subjecting theactivated alkaline ore with aeration in the presence of an alkalimetaphosphate and an anion-active ore is depressed and recovcollectingagent selected from the group consisting of fatty acids, rosin acids andsoaps derived from such acids, whereby siliceous gangue is floated andbeneflciated iron ore is depressed and recovered.

12. A process for the beneficiation of iron ores which iron oxide orepulp in the presence of lime, then removing excess soluble calciumcompounds from the a t v pulp by washing with water and incorporatingtherein sufllcient caustic soda to establish a strongly alkaline pH of10 to 12, thereafter subjecting the activated alkaline ore pulp toagitation with aeration in, the presence of talloel and sodiumhexametaphosphate whereby siliceous gangue is floated and beneficiatediron ore is depressed and recovered.

13, A process for the beneflciation oi iron ores alkaline pH of 10 to12, there-- siliceous gangue is floated,

comprises blunging an aqueous comminuted which comprises blunging anaqueous commiluuted'- which comprises comminuting, to mesh in thepresence of asoluble lime salt, such an orc containing also quartz andcalcite, adjusting the solids content of the resulting pulp to 20 percent, incorporating in the pulp per ton of ore about 2 pounds of sodiumhydroxide, about 0.8 pound of sodium hexametaphosphate and about 0.8pound of. talloel; agitating the resulting mixture for about fourminutes to condition the pulp, agitating and aerating the conditionedpulp for about five minutes, removing a froth product con tainingquartz, recovering an initial residue from the treated pulp containingiron ore of reduced quartzcontent, again agitating and aerating thequartz-containing froth product with additional quantities of the samereagents and water to further separate quartz in the froth and depress amiddling residue of iron ore in the pulp, and combining said initialresidue and-middling residue to yield a beneflciated iron ore of reducedsilica content. p

. 14. A process for the beneficiation of an oxidized iron ore whichcomprises comminuting such an ore in the presence of water and lime,adjusting the alkalinity of the resulting pulp to a pH at wherebysiliceous gangue is floated and removed,

and beneficiated iron ore is "depressed and recovered.

15.' A process in accordance with claim 14 wherein tolloel is employedas the anionic collecting agent.

1d. A process inaccordance with claim 14 wherein oleic acid is employedas the anionic collecting agent.

.17. A process in accordance-with claim 14 wherein a fatty acid ,soap isemployed as the anionic collecting agent.

18. A process in accordance with claim 14 wherein a solublepyrophosphate is also incorporated in the pulp, whereby calcareousgangue is floated and removed with the siliceous gangue.

19. A process in accordance with claim 14 wherein soda ash isincorporated in the prepared ore pulp to secure the desired alkalinityand precipitate excess lime salts.

JULIUS BRUCE CLEMMER. BAI-LARD H. CLEMMONS.

